Aluminous abrasive.



L. E. SAUNDERS L H.KH. WHITE.

ALUlVllNOUS ABRASIVE.

APPLICATION FILED DEC. 25 |917- Ato amarre PATENT orrtpnm LEWIS E. SAUNDEIRS AND RAY HILL WHITE, NIAGARA FALLS, NEW YORK,

ASSIGNORSTO NORTON COMPANY, OF WORCESTER, MASSACHUSETTS, A COR- JEORATION OF MASSACHUSETTS.

ALUMINOUS ABRASIVE.

Specification. of Letters Patent.

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x To all/:cham 1t/may concern All omd, of compounds of'oneor more of the` alkali metals, especially sodium and potas-` Be it known that we, Lewis E. SAUNDnRs and RAY HILL WHITE, .citizens of the United States, residing at Niagara Falls, 1n the county of Niagara and State of New York,

have invented certain new and useful lmprovements in Aluminous Abrasives, of which the following is a specification.

This invention relates to a novel crystalline aluminous abrasive containing material proportions of an acid oXid of the silica type, but characterized by a weak grainstructure due to alkali.

It is now well understood by those familiar with electric furnace abrasives of the alumina class that silica in relatively small proportions, say up to four or five per cent., exerts a marked strengthening and toughening action upon the alumina grain, the resulting product being well adapted for certain types of work, but less suited for other operations, such as polishing metals and the like, for which a suciently hard but structurally weak grain is required. In the above` respect titanium oxid acts substantially like silica, and both oXids are herein referred `to .as acid-oxide. Iron oxid, on the other hand,l is practically neutral in so far-as its e'ect upon the character of the grain is concerned. y

Our researches have shown that the toughening and strengthenin eect heretofore regarded as characteristlc of silica in )such `proportions as indicated above, may beneutrallzed toany desired degree, or completely, by the presence in the finished grain, in proper proportions relatively to the acid sium. In the light of this discovery, we

have' been enabled, by properly adjusting alli the amountv of alkali in a charge of silicious alumina toproduce therefrom an. electric furnace abrasive of weak structure, and ossessing special advantages for metal polishin and similar purposes. Furthermore, by

.suitably adjusting the alkali-content of the charge to its content of acid-om'd we are enl abled to vary the'guality ofthe grain at will between) rather wide limits.A This is of advantage in the art because it 'permits the employment of silicious alumina from any source for the manufacture of abrasives of 1 weak grain structure, a result not heretofore attainable by any known means.

The nature of the effects due to the introduction of varyingl proportions of soda into a charge of silicious alumina are illustrated in the accompanying'drawing, comprising a series of curves exhibiting graphically the effect of composition of the charge upon strength of grain.

The curve indicated by the numeral l illustrates the increasing strength of grain with increasing silica-content up to three per cent., no alkali having been added to the charge, and the quantity of alkali present in the charge before fusion being merely that normally carried by commercially pure alumina, that is to say, in the neighborhood of one per cent. 'lhe scale used to represent the grain strength is arbitrary, but it will be observed that additions of silica amounting only to three per cent. vhave resulted in a marked increase in' the strength of grain,

f associated with live per cent. of addedsoda (indicated by the point A) is actually weaker than that made from a silica-free alumina to which no alkali addition has been made (indicated by the point B). ln

other words, the alkali addition has in this case `entirely overbalance/d the strengthening action of the silica. Similarly, itwill be noted .thata product derived from a charge containing three per cent. .of sllica associated with'two and one-half per cent. of

added alkali (point C on the curve Il) is practically comparable, so far as strength of grain 1s concerned, with a product derived from substantially pure alumina (point B on curve I). It will thus be seen that on theA basis of these curves, products showin an extremely wide' variation in Astrengt of grain may be prepared at will,

even ,though the alumina serving as the raw material is associated with material amounts [of silica.

Curve IV shows graphically the e'ect of increasing additions of soda in weakening the grain prepared from a charge containing three per cent.- of silica, the curve covering p kali-content, if any, of the raw material 'while this material may vary rather widely used. For example, one suitable raw material for the practice of the present process in silicious alumina derived from alunite;

in composition according to the method used in its preparation, and the care employed, it usually contains from three to eight per cent. of silica; in the neighborhood of one per cent. of iron oXid; and from one to three per cent. of alkali calculated as lcharacter of the pro-duct. .alkali is of course to be expected in furnac- KzO. f The furnacing operation is carried outl under temperature conditions to avoid, as far as may be practicable,l the elimination of the alkali by volatilization, inasmuch as the relative content of alkali and acid-oxid is a controllingfactor in determining the Some loss of ing at a temperature suiiicient to fuse the alumina, but the alkali-content of the charge is readily adjusted in such manner as to yield a product of the character desired. Generally speaking, it has been observed that the loss of alkali in the furnacing operation ranges between thirty and fifty per cent. of the total quantity in the charge.

. In a copending application Serial No. 152,099,led March 2,1917,we have pointed out that alkali'additions made insmall. proportions to substantially pure alumina', followed by fusion in the electric furnace, yield*- a. product characterized by thel presence of materlal proportions of alumina in the crystal form which is now known as the beta modification. This transformation of alumina to the beta modification has not been observed to any material extent where the alkali addition is made in like small proportions to silicious alumina. However, by sufficient addition of alkali the charge may be more or less completely transformed to the beta modification. For example, the composition indicated at the point A of curve III contained approximately fifty per cent. of beta-alumina.

In other Words, the acid-oxide SiO2 and Ti02, and alkali, co-act in such manner that the alkali is capable of neutralizing the normal grain-strengthening eect of the acidoxids; while on the other hand, the acidoxids when present in sufcent proportion are capable of inhibiting the transformation of alumina into the beta modification. By a proper proportioning of these components it is clear therefore that a wide variety of crystalline aluminous products may be prepared, with adaptation of the product to special uses in the abrasive art.

As stated above, Ti()2 is to be regarded as equivalent to SiO2 for the purposes of this invention, both in its toughening and strengthening effect upon the alumina grains, and in respect to the neutralization of this effect by the alkali.

. We claim v 1. A crystalline aluminous abrasive'characterized by the presence therein of material amounts of an acid-oXid and an alkali, these components so proportioned as to yield a relativelyv weak abrasive grain as compared with aluminous grains of like acidoXid content but substantially free from alkali.,

`2. A crystalline aluminous abrasive characterized by thepresence therein of material amounts vof silica and an alkali, these components so proportioned as to yield a relatively weak abrasive grain as compared with aluminous grains of like silica-content but substantially free from alkali.

' In testimony whereof we affix our signatures.

LEWIS E. SAUNDERS. RAY HILLWHITE.

Correeogxin Leiters Patent No. 1,263,607.

It is hereby certified that in Letters Patent No. 1,263,607, granted April 23, 1918, upon the application oi Lewis E. Seunders'and Ray Hill White, of Niagara Falls, New York, for an improvementin Aluminous Abrasives, an error appears y in tile printedy specification requiring correction as follows: Page l2, line 20, for the Word in, reed is; andthat the said Letters Patent should be reed'with this cor rection therein that the same may conform to therecord of the case in the-Patent @Hice Signed and ysealed this 14th day of May, A, D.. 191,8.

[SEAL] R. F. WHITEHEAD,

Acting Commissioner of Patents. 

